The present invention relates to a multiple throttle apparatus to open and close a plurality of throttle valves which are disposed at the air intake passage of an engine. More particularly, it relates to a multiple throttle apparatus having a throttle valve at an air intake passage of each cylinder of an engine which is mounted on a motorcycle, or other high performance engine vehicle.
As a conventional throttle apparatus mounted on a four-wheel car, an electronically controlled throttle apparatus or a wire-operated and electronically controlled throttle apparatus are known.
For example, the structure of a wire-operated and electronically controlled throttle apparatus is disclosed in Japanese Patent Laid-open H6-207535 as follows. With the air intake unit for a six-cylinder V-type engine comprising two surge tanks which collect the air intake passages provided for each cylinder three each and air intake passages extending upstream from each surge tank, two throttle valves disposed at each upstream air intake passage are linked with a single throttle shaft and driven by a single wire to open and close. Then, when traction control is performed, the throttle valves are driven by a single motor to the closing direction.
For another example and as disclosed in Japanese Patent Laid-open H8-218904, there is a throttle apparatus, with throttle valves each respectively disposed to two air intake passages which are formed in a throttle body and linked so as to be free to pivot with a throttle shaft and driven to open and close by a motor which is disposed at an end side of the throttle shaft.
With the above-mentioned apparatus, since the conventional throttle apparatus is disposed at the upstream side of a surge tank or the upstream side of a relatively long air intake passage, the air controlled by an open and close operation of the throttle valve flows into an air intake passage (an air intake port) corresponding to each cylinder after being stored in a surge tank or after passing through a long intake passage. Therefore, air amount flowing into an engine cylinder does not change much in accordance with a small open and close movement of the throttle valve. Accordingly, a fine open and close control is not effective.
On the other hand, as a throttle apparatus which is mounted on a motorcycle, or other such like high performance engine vehicle, a multiple throttle apparatus is known because the responsibility of throttle operation is considered important. With this apparatus, a throttle valve is disposed to each air intake passage corresponding to each cylinder (each air intake port) at the position close to the air intake port of a cylinder head. Each throttle shaft supporting each throttle valve free to pivot is linked together with synchronize levers, urge springs, and so on to transmit torque, and all throttle valves are driven to open and close by a single wire. Further, to perform idle speed control (ISC) of the engine, a separate ISC valve is disposed to or associated with this apparatus.
By the way, even for an engine mounted to a motorcycle, etc. an electronic control which drives a plurality of throttle valves with a motor is contemplated. Further, it is also contemplated to eliminate a separate ISC valve by controlling idle speed with fine adjustment of the opening angle of the throttle valve.
Further, throttle operation of a motorcycle is more sensitive than that of a four-wheel car and is accompanied with rapid changes. Therefore, it is desired to ensure safe driving without rapid drive operation, etc. by controlling power at adequate conditions while improving performance, even in a situation when the driver mishandles the throttle or when the road conditions, etc. are poor.